When the brain is functioning as it should, we tend to feel good and are able to cope confidently and securely with the ups and downs in our daily lives. However, when the level of neurotransmitters fluctuates, normal functions are impaired.

A lack of certain neurotransmitters is thought to cause depression, but studies have yet to determine what causes the neurotransmitter activity to drop. Genetics, stress, major life event changes, chronic illness, medications, hormone changes, and light exposure are all thought to play a role.

Diagnosing SAD and other types of depression is often difficult. Unlike physical ailments, which can be identified through tests that measure levels of organ function or chemical imbalances, depression can only be diagnosed with a thorough medical and personal history, complemented by a full medical work-up to rule out physical causes for the symptoms.